字符串

基本概念

字符串是一种用于表示文本序列的数据类型。字符串是由字符组成的不可变对象，这意味着一旦创建了一个字符串，你就不能改变它的内容。

常用字符串方法

Length：获取字符串长度

string str = "Hello";
Console.WriteLine(str.Length); // 输出: 5

Substring：返回从指定索引开始的子字符串

string str = "Hello World";
string subStr = str.Substring(6);
Console.WriteLine(subStr); // 输出: "World"

Concat：将两个或多个字符串连接在一起

string result = string.Concat("Hello", " ", "World");
Console.WriteLine(result); // 输出: "Hello World"

Format：格式化字符串

string formattedString = string.Format("{0} {1}", "Hello", "World");
Console.WriteLine(formattedString); // 输出: "Hello World"

Join：将字符串数组连接成一个字符串，以指定的分隔符分隔

string[] words = { "Hello", "World" };
string joinedString = string.Join(", ", words);
Console.WriteLine(joinedString); // 输出: "Hello, World"

Replace：替换字符串中的子字符串

string originalString = "Hello World";
string replacedString = originalString.Replace("World", "Universe");
Console.WriteLine(replacedString); // 输出: "Hello Universe"

Split：将字符串分割成子字符串数组

string sentence = "Hello World from CSharp";
string[] words = sentence.Split(' ');
foreach (string word in words)
{
    Console.Write(word);
}
// 输出:HelloWorldfromCSharp

Contains:检查字符串是否包含指定的子字符串

string str = "Hello World";
bool containsWorld = str.Contains("World");
Console.WriteLine(containsWorld); // 输出: True

ToLower / ToUpper:转换字符串的大小写

string str = "Hello World";
string lowerCaseStr = str.ToLower();
string upperCaseStr = str.ToUpper();
Console.WriteLine(lowerCaseStr); // 输出: "hello world"
Console.WriteLine(upperCaseStr); // 输出: "HELLO WORLD"

Compare / CompareTo:比较两个字符串

string str1 = "Hello";
string str2 = "World";
int comparisonResult = str1.CompareTo(str2);
Console.WriteLine(comparisonResult < 0); // 输出: True

Equals / ReferenceEquals:检查两个字符串是否相等

string str1 = "Hello";
string str2 = "Hello";
bool areEqual = string.Equals(str1, str2);
Console.WriteLine(areEqual); // 输出: True

代码示例

static void Main(string[] args)
        {
           //字符串，字符串连接
            string fname, lname;
            fname = "Rowan";
            lname = "Atkinson";

            string fullname = fname + lname;
            Console.WriteLine("Full Name: {0}", fullname);

            //通过使用 string 构造函数
            char[] letters = { 'H', 'e', 'l', 'l','o' };
            string greetings = new string(letters);
            Console.WriteLine("Greetings: {0}", greetings);

            //方法返回字符串
            string[] sarray = { "Hello", "From", "Tutorials", "Point" };
            string message = String.Join(" ", sarray);
            Console.WriteLine("Message: {0}", message);

            //用于转化值的格式化方法
            DateTime waiting = new DateTime(2012, 10, 10, 17, 58, 1);
            string chat = String.Format("Message sent at {0:t} on {0:D}", 
            waiting);
            Console.WriteLine("Message: {0}", chat);
            Console.ReadKey() ;
        }